/Engine/Source/Runtime/Experimental/Chaos/Public/Chaos/Collision/CollisionConstraintAllocator.h
Return a midphase for a particle pair if it already exists, otherwise return null
[FParticlePairMidPhase](API\Runtime\Chaos\Chaos\Collision\FParticlePairMidPhase) * FindMidPhase ( [FGeometryParticleHandle](API\Runtime\Chaos\Chaos\FGeometryParticleHandle) * Particle0, [FGeometryParticleHandle](API\Runtime\Chaos\Chaos\FGeometryParticleHandle) * Particle1, [FGeometryParticleHandle](API\Runtime\Chaos\Chaos\FGeometryParticleHandle) * SearchParticlePerformanceHint )